Solutions

Definitions

• Solution - Solution - homogeneous mixture

Solvent Solvent - present in greater amount and dissolves solute

Solute Solute - substance that dissolves in a solvent and is said to be soluble

Universal Solvent is Water b/c almost everything dissolves in water

Most common solvent among liquids is water

Solute Solute - KMnO4 Solvent Solvent - H2O

Solvation- process of dissolving

solute particles are separated and pulled into solution (microscopic level)

solute particles are surrounded by solvent particles

Solvation- process of dissolvingIf you shake or stir the solution it increases the rate of solvation by breaking up solute and surrounding it with solvent

What else can speed up the rate of solvation?

““Like Dissolves Like”Like Dissolves Like”

Oil on your clothes?Oil on your clothes?

““Like Dissolves Like”Like Dissolves Like”

Oil on your clothes?Oil on your clothes?

NONPOLAR

NONPOLAR

POLAR

POLAR

““Like Dissolves Like”Like Dissolves Like”

Non polar solutes are more soluble Non polar solutes are more soluble in nonpolar solventsin nonpolar solvents

““Like Dissolves Like”Like Dissolves Like”

Non polar solutes are more soluble Non polar solutes are more soluble in nonpolar solventsin nonpolar solvents

NONPOLAR

NONPOLAR

POLAR

POLAR

““Like Dissolves Like”Like Dissolves Like”

Polar dissolves PolarPolar dissolves Polar

Ex. water dissolves salts (ionic & polar Ex. water dissolves salts (ionic & polar molecules)molecules)

““Like Dissolves Like”Like Dissolves Like”

Polar dissolves PolarPolar dissolves Polar

Ex. water dissolves salts (ionic & polar Ex. water dissolves salts (ionic & polar molecules)molecules)

Solvation

• Soap/DetergentSoap/Detergent– polar “head” with long nonpolar “tail”– dissolves nonpolar grease in polar water

Electrolyte- solution that conducts electricity

StrongElectrolyte

Non-Electrolyte

solute exists asions only

- +

salt

- +

sugar

solute exists asmolecules

only

- +

acetic acid

WeakElectrolyte

solute exists asions and

molecules DISSOCIATION IONIZATION

View animation online.

Solubility- the amount of solute that dissolves in given volume of solvent

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

Solubility- the amount of solute that dissolves in given volume of solvent

SATURATED SOLUTION(no more

solute dissolves)

UNSATURATED (dilute)

Small amt. of solute

dissolved

SUPERSATURATED Increase temp. to

dissolve more solute

concentration

Solubility

• SolubilitySolubility– maximum grams of solute that will dissolve in

100 g of solvent at a given temperature– varies with temp– based on a saturated solution

Definitions

• Soluble- any substance that dissolves in something else

• Insoluble- Any substance that does not dissolve

Definitions

• Miscible – one liquid dissolves in another liquid (ex. 2 polar liquids will be miscible)

• Immiscible – one liquid does not dissolve in another liquid (ex. oil and water) don’t mix b/c oil nonpolar and water polar

Definitions

• Alloy one metal dissolved in another

Solubility Curve

• Solubility CurveSolubility Curve– shows the

dependence of solubility on temperature

Solubility• Solids are more soluble at...Solids are more soluble at...

– high temperatures.

• Gases are more soluble at...Gases are more soluble at...– low temperatures &– high pressures (Henry’s Law).– EX: soda can

Henry’s Law & Soft Drinks• Soft drinks contain “carbonated water”

carbon dioxide gas dissolved in water• Gas in liquid is more soluble if pressure

above liquid is high (under pressure)

• When bottle opened pressure of CO2

decreases and solubility of CO2 also decreases, according to Henry’s Law.

• Result, bubbles of CO2 escape from solution.

Solution and Concentration

Concentration- a measure of how Concentration- a measure of how much solute is dissolved in the solutionmuch solute is dissolved in the solution

Solution and Concentration

Concentration- a measure of how Concentration- a measure of how much solute is dissolved in the solutionmuch solute is dissolved in the solution

Range from Range from

dilutedilute saturated saturated supersaturated supersaturated

• ways of expressing concentrationways of expressing concentration

–Molarity(M): moles solute / Liter solution

–Mass percent (mass solute / mass of solution) x 100

–Molality (m) - moles solute / Kg solvent

Molarity(M) = moles solute

Liter solution

Calculate the molarity of the following solution125 ml which contains 2.50 g NaCl

Calculate the molarity of the following solution125 ml which contains 2.50 g NaCl Molarity = moles of solute Liter of solution

Calculate the molarity of the following solution125 ml which contains 2.50 g NaCl Molarity = moles of solute Liter of solution

First change grams to moles2.50 g NaCl x 1 mole NaCl = 0.0428 moles NaCl 58.44 g NaCl

Calculate the molarity of the following solution125 ml which contains 2.50 g NaCl Molarity = moles of solute Liter of solution

First change grams to moles2.50 g NaCl x 1 mole NaCl = 0.0428 moles NaCl 58.44 g NaCl

M= 0.0428 moles NaCl = 0.342 M NaCl 0.125 L

Calculate the mass of the solute in the solution750 cm cubed of CaCl2 solution which is 0.500 M Molarity = moles of solute Liter of solution

First change Molarity to moles

Calculate the mass of the solute in the solution750 cm cubed of CaCl2 solution which is 0.500 M (0.500 moles/1L)

Molarity = moles of solute Liter of solution

First change Molarity to moles0.500 moles = moles CaCl2 1 Liter .750 L

Calculate the mass of the solute in the solution750 cm cubed of CaCl2 solution which is 0.500 M(0.500moles/1L)

Molarity = moles of solute Liter of solution

First change Molarity to moles0.500 moles = moles CaCl2 1 Liter .750 L 0.500 moles x .750 L = moles CaCl2 1 Liter

Calculate the mass of the solute in the solution750 cm cubed of CaCl2 solution which is 0.500 M Molarity = moles of solute Liter of solution

First change Molarity to moles0.500 moles = moles CaCl2 1 Liter .750 L 0.500 moles x .750 L = moles CaCl2 1 Liter 0.500 moles x .750 L = 0.375 moles CaCl2 1 Liter

Calculate the mass of the solute in the solution750 cm cubed of CaCl2 solution which is 0.500 M Molarity = moles of solute Liter of solution

First change Molarity to moles0.500 moles = moles CaCl2 1 Liter .750 L 0.500 moles x .750 L = moles CaCl2 1 Liter 0.500 moles x .750 L = 0.375 moles CaCl2 1 Liter

Next convert moles to grams0.375 moles CaCl2 x 110.98 g CaCl2 = 41.6 g CaCl2

Calculate how many liters of solution can be made fromA 2.00 M solution using 60.0 g NaOH Molarity = moles of solute

Liter of solution

Calculate how many liters of solution can be made fromA 2.00 M solution using 60.0 g NaOH Molarity = moles of solute

Liter of solution

First change grams of NaOH to moles60.00 g NaOH x 1 mole NaOH = 1.50 moles NaOH 40.00 g NaOH

Calculate how many liters of solution can be made fromA 2.00 M solution using 60.0 g NaOH Molarity = moles of solute

Liter of solution

Next change Molaririty to moles/liter 2.0 M = 2moles/1L2.00 moles = 1.5 moles NaOH 1 Liter ? L

First change grams of NaOH to moles60.00 g NaOH x 1 mole NaOH = 1.50 moles NaOH 40.00 g NaOH

Calculate how many liters of solution can be made fromA 2.00 M solution using 60.0 g NaOH Molarity = moles of solute

Liter of solution

Next change Molaririty to moles/liter2.00 moles = 1.5 moles NaOH 1 Liter ? L ? L = 1.5 moles NaOH x 1 Liter 2.0 moles

First change grams of NaOH to moles60.00 g NaOH x 1 mole NaOH = 1.50 moles NaOH 40.00 g NaOH

Calculate how many liters of solution can be made fromA 2.00 M solution using 60.0 g NaOH Molarity = moles of solute

Liter of solution

Next change Molaririty to moles/liter2.00 moles = 1.5 moles NaOH 1 Liter ? L ? L = 1.5 moles NaOH x 1 Liter 2.0 moles L= 0.750 liter

First change grams of NaOH to moles60.00 g NaOH x 1 mole NaOH = 1.50 moles NaOH 40.00 g NaOH

Concentration: Molarity Example•How would you prepare the following solution?

1.00 L of a 1.80 M aqueous solution of MgCl2

Molarity(M) = moles solute Liter solution

Concentration: Molarity Example•How would you prepare the following solution?

1.00 L of a 1.80 M aqueous solution of MgCl2

1.80 M = 1.8 mol MgCl2

1.00 L H20

Concentration: Molarity Example•How would you prepare the following solution?

1.00 L of a 1.80 M aqueous solution of MgCl2

1.80 M = 1.8 mol MgCl2

1.00 L H20

1.8 mol MgCl2 x 95.21 g MgCl2 = 171.38 g MgCl2

1 mol MgCl2

Take 171.38 g MgCl2 add water until you reach 1 liter

Concentration: Molarity Example•How would you prepare the following solution?

1 L of a 2.05 M aqueous solution of MgCl2

2.05 M = 2.05 mol MgCl2

1.0 L H20

2.05 mol MgCl2 x 95.21 g MgCl2 = 195.18 g MgCl2

1 mol MgCl2

Take 195 g MgCl2 add water until you reach 1 liter

Concentration: Molarity Example0.435 g of KMnO4 in 250. mL of solution, what is the molarity of KMnO4?

Molarity(M) = moles solute Liter solution

Concentration: Molarity Example0.435 g of KMnO4 in 250. mL of solution, what is the molarity of KMnO4?

first step convert the mass of material to

moles.

0.435 g KMnO4 • 1 mol KMnO4 = 0.00275 mol KMnO4

158.0 g KMnO4

Concentration: Molarity Example0.435 g of KMnO4 in 250. mL of solution, what is the molarity of KMnO4?

Now convert 250 ml to L

250 mL = 0.250 L

0.435 g KMnO4 • 1 mol KMnO4 = 0.00275 mol KMnO4

158.0 g KMnO4

Concentration: Molarity Example0.435 g of KMnO4 in 250. mL of solution, what is the molarity of KMnO4?

0.435 g KMnO4 • 1 mol KMnO4 = 0.00275 mol KMnO4

158.0 g KMnO4

Molarity KMnO4 = 0.00275 mol KMnO4 = 0.0110 M

0.250 L solution

Concentration: Molarity Example0.435 g of KMnO4 in 250. mL of solution, what is the molarity of KMnO4?

Now that the number of moles of substance is known, this can be combined with the volume of solution — which must be in liters — to give the molarity. Because 250. mL is equivalent to 0.250 L .

As is almost always the case, the first

step is to convert the mass of material to

moles.

0.435 g KMnO4 • 1 mol KMnO4 = 0.00275 mol KMnO4

158.0 g KMnO4

Molarity KMnO4 = 0.00275 mol KMnO4 = 0.0110 M

0.250 L solution

Lowering the concentration by adding solvent (water)

The amount of solute remains constant before and after the dilution but there is more solvent:

moles BEFORE = moles AFTER

C1V1 = C2V2

Suppose you have 0.500 M sucrose stock solution. How do you prepare 250 mL of 0.348 M sucrose solution ?

Concentration 0.500 M Sucrose

250 mL of 0.348 M sucrose

Dilution

A bottle of 0.500 M standard sucrose stock solution is in the lab.

Give precise instructions to your assistant on how to use the stock solution to prepare 250.0 mL of a

0.348 M sucrose solution.

A bottle of 0.500 M standard sucrose stock solution is in the lab.

Give precise instructions to your assistant on how to use the stock solution to prepare 250.0 mL of a

0.348 M sucrose solution.

Dilution Formula and Calculations

Mi x Vi = Mf x Vf How to make dilutions from concentrated stock Solve for VOLUME

What volume of 6.00M HCl must be diluted to obtain 5.00L of 1.50M HCl? Initial concentration of HCl Mi = 6.00M

Final concentration of HCl Mf = 1.50M

Final volume of solution Vf = 5.00L

6.00 M x Vi = 1.50 M x 5.00 L

Vi = 1.25 L

To make the desired quantity of diluted HCl, the chemist should begin with 1.25L of the concentrated solution and add enough water to bring the volume up to 5.00 L.

Dilution Formula and Calculations

Mi x Vi = Mf x Vf

Solve for MOLARITY

If you add 25 ml of water to 100 ml of KCl with a .30 M KCl what will the molarity of the diluted solution be? Initial concentration of KCl Mi = 0.30 M

Initial volume of KCl = 100 ml Final concentration of KCl Mf = ? M

Final volume of solution Vf = 100 + 25 = 125 ml

0.30 M x 100 ml = ?M x 125 ml 0.30 M x 100 ml = ?M 125 ml

Mf = 0.24 M

Factors Affecting Solubility1. Nature of Solute / Solvent1. Nature of Solute / Solvent.

2. Temperature -2. Temperature -

3. Pressure Factor (gas)3. Pressure Factor (gas)4. Size of Particle

5. Stirring mixture

Factors Affecting Solubility1. Nature of Solute / Solvent1. Nature of Solute / Solvent. - Like dissolves like (IMF)

2. Temperature -2. Temperature -i) Solids/Liquids- Solubility increases with Temperature

Increase K.E. increases motion and collision between solute / solvent.

ii) gas - Solubility decreases with Temperature

Increase K.E. result in gas escaping to atmosphere.

3. Pressure Factor -3. Pressure Factor -i) gas - Solubility increases with Pressure.

Increase pressure squeezes gas solute into solvent.

Solubilities of Solids vs TemperatureSolubilities of several ionic solid as a function of temperature.

MOST salts have greater solubility in hot water.

That is increasing temperature increases solubility of salts

Colligative Properties

Colligative Properties are properties of a liquid that change when a solute is added.

Colligative Properties

Dissolving solute in pure liquid will change all physical properties of liquid, Density, Vapor Pressure, Boiling Point, Freezing Point,Osmotic Pressure

Colligative Properties

The magnitude of the change depends on the numbernumber of solute particles in the solution, NOT on the identityidentity of the solute particles.

Boiling Point ElevationWhen solute is added, Boiling Point increases over Normal BPBoiling point is elevated because solute interferes with solvent forming into vapor.

Boiling Point Elevation

Some Boiling Point Elevation and Freezing Point Depression Constants

Normal bp (°C) Kb Normal fp (°C) Kf

Solvent pure solvent (°C/m) pure solvent (°C/m)

Water Water 100.00100.00 +0.5121 +0.5121 0.0 0.0 1.861.86BenzeneBenzene 80.10 80.10 +2.53+2.53 5.50 5.50 4.904.90CamphorCamphor 207 207 +5.611 +5.611 179.75 179.75 39.739.7Chloroform Chloroform 61.70 61.70 +3.63+3.63 - 63.5 - 63.5 4.70 4.70 (CH(CH33Cl)Cl)

Some Boiling Point Elevation and Freezing Point Depression Constants

Normal bp (°C) Kb Normal fp (°C) Kf

Solvent pure solvent (°C/m) pure solvent (°C/m)

Water Water 100.00100.00 +0.5121 +0.5121 0.0 0.0 1.861.86BenzeneBenzene 80.10 80.10 +2.53+2.53 5.50 5.50 4.904.90CamphorCamphor 207 207 +5.611 +5.611 179.75 179.75 39.739.7Chloroform Chloroform 61.70 61.70 +3.63+3.63 - 63.5 - 63.5 4.70 4.70 (CH(CH33Cl)Cl)

Solute particles do not fit into the crystal lattice of the solvent because of the differences in size. The solute essentially blocks the solvent from fitting into the crystal lattice during the freezing process.

Freezing Point DepressionFP is depressed (lowered) when solute blocks

solvent from crystallizing.

Dissolution at the molecular level?• Consider the dissolution of NaOH in H2O

Temperature & the Solubility of GasesThe solubility of gases DECREASES at higher temperatures

Vapor Pressure Lowering for a Solution

• The diagram below shows how a phase diagram is affected by dissolving a solute in a solvent.

• The black curve represents the pure liquid and the blue curve represents the solution.

• Notice the changes in the freezing & boiling points.

Vapor Pressure Lowering

• The presence of a non-volatile solute means that fewer solvent particles are at the solution’s surface, so less solvent evaporates!

Application of Vapor Pressure Lowering

• Describe what is happening in the pictures below.• Use the concept of vapor pressure lowering to

explain this phenomenon.

Osmotic pressure• Osmosis is the spontaneous movement of water across a semi-

permeable membrane from an area of low solute concentration to an area of high solute concentration

• Osmotic Pressure - The Pressure that must be applied to stop osmosis

= i CRT

where P = osmotic pressure i = van’t Hoff factor C = molarity R = ideal gas constant T = Kelvin temperature

Osmosis and Blood Cells(a) A cell placed in an isotonic solution. The net movement of water in and out of the cell is zero because the concentration of solutes inside and outside the cell is the same.

(b) In a hypertonic solution, the concentration of solutes outside the cell is greater than that inside. There is a net flow of water out of the cell, causing the cell to dehydrate, shrink, and perhaps die.

(c) In a hypotonic solution, the concentration of solutes outside of the cell is less than that inside. There is a net flow of water into the cell, causing the cell to swell and perhaps to burst.Isotonic solution Hypertonic solution Hypotonic solution